Combined closed loop/open loop power control in a time division duplex communication system

ABSTRACT

Combined closed loop/open loop power control controls transmission power levels in a spread spectrum time division duplex communication station. The first station transmits power commands based on in part a reception quality of the received communications. The first station transmits a first communication having transmission power commands based on in part a reception quality of the received communications. The first station transmits a first communication having a transmission power level in a first time slot. The second station received the first communication and the power commands. A power level of the first communication as received is measured. A path loss estimate is determined based on in part the measured received first communication power level and the first communication transmission power level. The second station transmits a first communication to the first station in a first time slot. The second communication transmission power level is set based on in part the path loss estimate weighted by a factor and power commands. The factor is a function of a time separation of the first and second time slots.

BACKGROUND

This invention generally relates to spread spectrum time division duplex(TDD) communication systems. More particularly, the present inventionrelates to a system and method for controlling transmission power withinTDD communication systems.

FIG. 1 depicts a wireless spread spectrum time division duplex (TDD)communication system. The system has a plurality of base stations 30₁-30 ₇. Each base station 30 ₁ communicates with user equipments (UEs)32 ₁-32 ₃ in its operating area. Communications transmitted from a basestation 30 ₁ to a UE 32 ₁ are referred to as downlink communications andcommunications transmitted from a UE 32 ₁ to a base station 30 ₁ arereferred to as uplink communications.

In addition to communicating over different frequency spectrums, spreadspectrum TDD systems carry multiple communications over the samespectrum. The multiple signals are distinguished by their respectivechip code sequences (codes). Also, to more efficiently use the spreadspectrum, TDD systems as illustrated in FIG. 2 use repeating frames 34divided into a number of time slots 36 ₁-36 _(n,), such as fifteen timeslots. In such systems, a communication is sent in selected time slots36 ₁-36 _(n) using selected codes. Accordingly, one frame 34 is capableof carrying multiple communications distinguished by both time slot 36₁-36 _(n) and code. The combination of a single code in a single timeslot is referred to as a resource unit. Based on the bandwidth requiredto support a communication, one or multiple resource units are assignedto that communication.

Most TDD systems adaptively control transmission power levels. In a TDDsystem, many communications may share the same time slot and spectrum.When a UE 32 ₁ or base station 30 ₁ is receiving a specificcommunication, all the other communications using the same time slot andspectrum cause interference to the specific communication. Increasingthe transmission power level of one communication degrades the signalquality of all other communications within that time slot and spectrum.However, reducing the transmission power level too far results inundesirable signal to noise ratios (SNRs) and bit error rates (BERs) atthe receivers. To maintain both the signal quality of communications andlow transmission power levels, transmission power control is used.

One approach to control transmission power levels is open loop powercontrol. In open loop power control, typically a base station 30 ₁transmits to a UE 32 ₁ a reference downlink communication and thetransmission power level of that communication. The UE 32 ₁ receives thereference communication and measures its received power level. Bysubtracting the received power level from the transmission power level,a pathloss for the reference communication is determined. To determine atransmission power level for the uplink, the downlink pathloss is addedto a desired received power level at the base station 30 ₁. The UE'stransmission power level is set to the determined uplink transmissionpower level.

Another approach to control transmission power level is closed looppower control. In closed loop power control, typically the base station30 ₁ determines the signal to interference ratio (SIR) of acommunication received from the UE 32 ₁. The determined SIR is comparedto a target SIR (SIR_(TARGET)). Based on the comparison, the basestation 30 ₁ transmits a power command, b_(TPC). After receiving thepower command, the UE 32 ₁ increases or decreases its transmission powerlevel based on the received power command.

Both closed loop and open loop power control have disadvantages. Undercertain conditions, the performance of closed loop systems degrades. Forinstance, if communications sent between a UE and a base station are ina highly dynamic environment, such as due to the UE moving, such systemsmay not be able to adapt fast enough to compensate for the changes. Theupdate rate of closed loop power control in TDD is 100 cycles per secondwhich is not sufficient for fast fading channels. Open loop powercontrol is sensitive to uncertainties in the uplink and downlink gainchains and interference levels.

One approach to combining closed loop and open loop power control wasproposed by the Association of Radio Industries and Business (ARIB) anduses Equations 1, 2, and 3.

T _(UE) =P _(BS)(n)+L  Equation 1

P _(BS)(n)=P _(BS)(n−1)+b _(TPC)Δ_(TPC)  Equation 2

$\begin{matrix}{b_{TPC} = \{ \begin{matrix}{1\text{:}\quad {if}\quad {SIR}_{BS}\quad {\langle\quad {SIR}_{TARGET}}} \\{{{1\text{:}\quad {if}\quad {SIR}_{BS}}\quad\rangle}\quad {SIR}_{TARGET}}\end{matrix} } & {{Equation}\quad 3}\end{matrix}$

T_(UE) is the determined transmission power level of the UE 32 ₁. L isthe estimated downlink pathloss. P_(BS)(n) is the desired received powerlevel of the base station 30 ₁ as adjusted by Equation 2. For eachreceived power command, b_(TPC), the desired received power level isincreased or decreased by Δ_(TPC). Δ_(TPC) is typically one decibel(dB). The power command, b_(TPC), is one, when the SIR of the UE'suplink communication as measured at the base station 30, SIR_(BS), isless than a target SIR, SIR_(TARGET). Conversely, the power command isminus one, when SIR_(BS) is larger than SIR_(TARGET).

Under certain conditions, the performance of these systems degrades. Forinstance, if communications sent between a UE 32 and a base station 30are in a highly dynamic environment, such as due to the UE 32 moving,the path loss estimate for open loop severely degrades the overallsystem's performance. Accordingly, there is a need for alternateapproaches to maintain signal quality and low transmission power levelsfor all environments and scenarios.

SUMMARY

Combined closed loop/open loop power control controls transmission powerlevels in a spread spectrum time division duplex communication station.The first station transmits power commands based on in part a receptionquality of the received communications. The first station transmits afirst communication having transmission power commands based on in parta reception quality of the received communications. The first stationtransmits a first communication having a transmission power level in afirst time slot. The second station received the second communicationand the power commands. A power level of the first communication asreceived is measured. A path loss estimate is determined based on inpart the measured received first communication power level and the firstcommunication transmission power level. The first station transmits afirst communication to the first station in a second time slot. Thesecond communication transmission power level is set based on in partthe path loss estimate weighted by a factor and power commands. Thefactor is a function of a time separation of the first and second timeslots.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art TDD system.

FIG. 2 illustrates time slots in repeating frames of a TDD system.

FIG. 3 is a flow chart of combined closed loop/open loop power control.

FIG. 4 is a diagram of components of two communication stations usingcombined closed loop/open loop power control.

FIGS. 5-10 depict graphs of the performance of a closed loop, ARIB'sproposal and two (2) schemes of combined closed loop/open loop powercontrol.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments will be described with reference to thedrawing figures where like numerals represent like elements throughout.Combined closed loop/open loop power control will be explained using theflow chart of FIG. 3 and the components of two simplified communicationstations 50, 52 as shown in FIG. 4. For the following discussion, thecommunication station having its transmitter's power controlled isreferred to as the transmitting station 52 and the communication stationreceiving power controlled communications is referred to as thereceiving station 50. Since combined closed loop/open loop power controlmay be used for uplink, downlink or both types of communications, thetransmitter having its power controlled may be located at a base station30 ₁, UE 32 ₁ or both. Accordingly, if both uplink and downlink powercontrol are used, the receiving and transmitting station's componentsare located at both the base station 30 ₁ and UE 32 ₁.

The receiving station 50 receives various radio frequency signalsincluding communications from the transmitting station 52 using anantenna 56, or alternately, an antenna array. The received signals arepassed through an isolator 60 to a demodulator 68 to produce a basebandsignal. The baseband signal is processed, such as by a channelestimation device 96 and a data estimation device 98, in the time slotsand with the appropriate codes assigned to the transmitting station'scommunication. The channel estimation device 96 commonly uses thetraining sequence component in the baseband signal to provide channelinformation, such as channel impulse responses. The channel informationis used by the data estimation device 98, the interference measurementdevice 90, the signal power measurement device 92 and the transmit powercalculation device 94. The data estimation device 98 recovers data fromthe channel by estimating soft symbols using the channel information.Using the soft symbols and channel information, the transmit powercalculation device 94 controls the receiving station's transmissionpower level by controlling the gain of an amplifier 76.

The signal power measurement device 92 uses either the soft symbols orthe channel information, or both, to determine the received signal powerof the communication in decibels (dB). The interference measurementdevice 90 determines the interference level in dB, I_(RS), within thechannel, based on either the channel information, or the soft symbolsgenerated by the data estimation device 98, or both.

The closed loop power command generator 88 uses the measuredcommunication's received power level and the interference level, I_(RS),to determine the Signal to Interference Ratio (SIR) of the receivedcommunication. Based on a comparison of the determined SIR with a targetSIR (SIR_(TARGET)), a closed loop power command is generated, b_(TPC),such as a power command bit, b_(TPC), step 38. Alternately, the powercommand may be based on any quality measurement of the received signal.

For use in estimating the path loss between the receiving andtransmitting stations 50, 52 and sending data, the receiving station 50sends a communication to the transmitting station 58, step 40. Thecommunication may be sent on any one of various channels. Typically, ina TDD system, the channels used for estimating path loss are referred toas reference channels, although other channels may be used. If thereceiving station 50 is a base station 30 ₁, the communication ispreferably sent over a downlink common channel or a common controlphysical channel (CCPCH). Data to be communicated to the transmittingstation 52 over the reference channel is referred to as referencechannel data. The reference data may include, as shown, the interferencelevel, I_(RS) multiplexed with other reference data, such as thetransmission power level of the reference channel, T_(RS). Theinterference level, I_(RS), and reference channel power level, T_(RS),may be sent in other channels, such as a signaling channel. The closedloop power control command, b_(TPC), is typically sent in a dedicatedchannel. The dedicated channel is dedicated to the communication betweenthe receiving station 50 and transmitting station 52, step 40.

The reference channel data is generated by a reference channel datagenerator 86. The reference data is assigned one or multiple resourceunits based on the communication's bandwidth requirements. A spreadingand training sequence insertion device 82 spreads the reference channeldata and makes the spread reference data time-multiplexed with atraining sequence in the appropriate time slots and codes of theassigned resource units. The resulting sequence is referred to as acommunication burst. The communication burst is subsequently amplifiedby an amplifier 78. The amplified communication burst may be summed by asum device 72 with any other communication burst created throughdevices, such as a data generator 84, spreading and training sequenceinsertion device 80 and amplifier 76.

The summed communication bursts are modulated by a modulator 64. Themodulated signal is passed through an isolator 60 and radiated by anantenna 56 as shown or, alternately, through an antenna array. Theradiated signal is passed through a wireless radio channel 54 to anantenna 58 of the transmitting station 52. The type of modulation usedfor the transmitted communication can be any of the those known to thoseskilled in the art, such as direct phase shift keying (DPSK) orquadrature phase shift keying (QPSK).

The antenna 58 or, alternately, antenna array of the transmittingstation 52 receives various radio frequency signals. The receivedsignals are passed through an isolator 62 to a demodulator 66 to producea baseband signal. The baseband signal is processed, such as by achannel estimation device 100 and a data estimation device 102, in thetime slots and with the appropriate codes assigned to the communicationburst of the receiving station 50. The channel estimation device 100commonly uses the training sequence component in the baseband signal toprovide channel information, such as channel impulse responses. Thechannel information is used by the data estimation device 102, a powermeasurement device 110 and a quality measurement device 114.

The power level of the processed communication corresponding to thereference channel, R_(TS), is measured by the power measurement device110 and sent to a pathloss estimation device 112, step 42. Both thechannel estimation device 100 and the data estimation device 102 arecapable of separating the reference channel from all other channels. Ifan automatic gain control device or amplifier is used for processing thereceived signals, the measured power level is adjusted to correct forthe gain of these devices at either the power measurement device 110 orthe pathloss estimation device 112. The power measurement device 110 isa component of the combined closed loop/open loop controller 108. Asillustrated in FIG. 4, the combined closed loop/open loop powercontroller 108 comprises the power measurement device 110, pathlossestimation device 112, quality measurement device 114, and transmitpower calculation device 116.

To determine the path loss, L, the transmitting station 52 also requiresthe communication's transmitted power level, T_(RS). The transmittedpower level, T_(RS), may be sent along with the communication's data orin a signaling channel. If the power level, T_(RS), is sent along withthe communication's data, the data estimation device 102 interprets thepower level and sends the interpreted power level to the pathlossestimation device 112. If the receiving station 50 is a base station 30₁, preferably the transmitted power level, T_(RS), is sent via thebroadcast channel (BCH) from the base station 30 ₁. By subtracting thereceived communication's power level, R_(TS) in dB, from the sentcommunication's transmitted power level, T_(RS) in dB, the pathlossestimation device 112 estimates the path loss, L, between the twostations 50, 52, step 44. In certain situations, instead of transmittingthe transmitted power level, T_(RS), the receiving station 50 maytransmit a reference for the transmitted power level. In that case, thepathloss estimation device 112 provides reference levels for the pathloss, L.

If a time delay exists between the estimated path loss and thetransmitted communication, the path loss experienced by the transmittedcommunication may differ from the calculated loss. In TDD systems wherecommunications are sent in differing time slots 36 ₁-36 _(n), the timeslot delay between received and transmitted communications may degradethe performance of an open loop power control system. Combined closedloop/open loop power control utilizes both closed loop and open looppower control aspects. If the quality of the path loss measurement ishigh, the system primarily acts as an open loop system. If the qualityof the path loss measurement is low, the system primarily acts as aclosed loop system. To combine the two power control aspects, the systemweights the open loop aspect based on the quality of the path lossmeasurement.

A quality measurement device 114 in a weighted open loop powercontroller 108 determines the quality of the estimated path loss, step46. The quality may be determined using the channel informationgenerated by the channel estimation device 100, the soft symbolsgenerated by the data estimation device 102 or other quality measurementtechniques. The estimated path loss quality is used to weight the pathloss estimate by the transmit power calculation device 116. If the powercommand, b_(TPC), was sent in the communication's data, the dataestimation device 102 interprets the closed loop power command, b_(TPC).Using the closed loop power command, b_(TPC), and the weighted pathloss, the transmit power calculation device 116 sets the transmit powerlevel of the receiving station 50, step 48.

The following is one of the preferred combined closed loop/open looppower control algorithms. The transmitting station's power level indecibels, P_(TS), is determined using Equations 4 and 6.

P _(TS) =P ₀ +G(n)+αL  Equation 4

P₀ is the power level that the receiving station 50 desires to receivethe transmitting station's communication in dB. P₀ is determined by thedesired SIR at the receiving station 50, SIR_(TARGET), and theinterference level, I_(RS), at the receiving station 50 using Equation5.

P ₀=SIR_(TARGET) +I _(RS)  Equation 5

I_(RS) is either signaled or broadcasted from the receiving station 50to the transmitting station 52. For downlink power control, SIR_(TARGET)is known at the transmitting station 52. For uplink power control,SIR_(TARGET) is signaled from the receiving station 50 to thetransmitting station 52. G(n) is the closed loop power control factor.Equation 6 is one equation for determining G(n).

G(n)=G(n−1)+b _(TPC)Δ_(TPC)  Equation 6

G(n−1) is the previous closed loop power control factor. The powercommand, b_(TPC), for use in Equation 6 is either +1 or −1. Onetechnique for determining the power command, b_(TPC), is Equation 3. Thepower command, b_(TPC), is typically updated at a rate of 100 ms in aTDD system, although other update rates may be used. Δ_(TPC) is thechange in power level. The change in power level is typically 1 dBalthough other values may be used. As a result, the closed loop factorincreases by 1 dB if b_(TPC) is +1 and decreases by 1 dB if b_(TPC) is−1.

The weighting value, α, is determined by the quality measurement device114. α is a measure of the quality of the estimated path loss and is,preferably, based on the number of time slots, D, between the time slotof the last path loss estimate and the first time slot of thecommunication transmitted by the transmitting station 52. The value of αis from zero to one. Generally, if the time difference, D, between thetime slots is small, the recent path loss estimate will be fairlyaccurate and α is set at a value close to one. By contrast, if the timedifference is large, the path loss estimate may not be accurate and theclosed loop aspect is most likely more accurate. Accordingly, α is setat a value closer to zero. Equations 7 and 8 are two equations fordetermining α, although others may be used.

α=1−(D−1)/(D _(max)−1)  Equation 7

α=max{1−(D−1)/(D _(max-allowed)−1),0}  Equation 8

D_(max) is the maximum possible delay. A typical value for a framehaving fifteen time slots is seven. If the delay is D_(max), α is zero.D_(max-allowed) is the maximum allowed time slot delay for using openloop power control. If the delay exceeds D_(max-allowed), open looppower control is effectively turned off by setting α=0. Using thecalculated transmit power level, P_(TS), determined by a transmit powercalculation device 116, the combined closed loop/open loop powercontroller 108 sets the transmit power of the transmitted communication.

Data to be transmitted in a communication from the transmitting station52 is produced by a data generator 106. The communication data is spreadand time-multiplexed with a training sequence by the spreading andtraining sequence insertion device 104 in the appropriate time slots andcodes of the assigned resource units producing a communication burst.The spread signal is amplified by the amplifier 74 and modulated by themodulator 70 to radio frequency.

The combined closed loop/open loop power controller 108 controls thegain of the amplifier 74 to achieve the determined transmit power level,P_(TS), for the communication. The power controlled communication ispassed through the isolator 62 and radiated by the antenna 58.

Equations 9 and 10 are another preferred combined closed loop/open looppower control algorithm.

P _(TS) =P ₀ +K(n)  Equation 9

K(n)=K(n−1)+b _(TPC) Δ_(TPC) +αL  Equation 10

K(n) is the combined closed loop/open loop factor. As shown, this factorincludes both the closed loop and open loop power control aspects.Equations 4 and 5 segregate the two aspects.

Although the two above algorithms only weighted the open loop factor,the weighting may be applied to the closed loop factor or both the openand closed loop factors. Under certain conditions, the network operatormay desire to use solely open loop or solely closed loop power control.For example, the operator may use solely closed loop power control bysetting α to zero.

FIGS. 5-10 depict graphs 118-128 illustrating the performance of acombined closed-loop/open-loop power control system. These graphs118-128 depict the results of simulations comparing the performance ofthe ARIB proposed system, a closed loop, a combined open loop/closedloop system using Equations 4 and 6 (scheme I) and a combined systemusing Equations 9 and 10 (scheme II). The simulations were performed atthe symbol rate. A spreading factor of sixteen was used for both theuplink and downlink channels. The uplink and downlink channels areInternational Telecommunication Union (ITU) Channel model [ITU-R M.1225,vehicular, type B]. Additive noises were simulated as being independentof white Gaussian noises with unity variance. The path loss is estimatedat the transmitting station 52 which is a UE 32 ₁ and in particular amobile station. The BCH channel was used for the path loss estimate. Thepath loss was estimated two times per frame at a rate of 200 cycles persecond. The receiving station 50, which was a base station 30 ₁, sentthe BCH transmission power level over the BCH. RAKE combining was usedfor both the UE 32 ₁ and base station 30 ₁. Antenna diversity combiningwas used at the base station 30 ₁.

Graphs 118, 122, 126 depict the standard deviation of the receivedsignal to noise ratio (SNR) at the base station 30 ₁ of the UE's powercontrolled communication as a function of the time slot delay, D. Graphs120, 124, 128 depict the normalized bias of the received SNR as afunction of the delay, D. The normalization was performed with respectto the desired SNR. Each point in the graphs 118-128 represents theaverage of 3000 Monte-Carlo runs.

Graphs 118, 120 depict the results for an a set at one. For low timeslot delays (D<4), scheme I and II outperform closed loop power control.For larger delays (D≧4), closed loop outperforms both scheme I and IIwhich demonstrates the importance of weighting the open loop and closedloop aspects.

Graphs 122, 124 depict the results for an α set at 0.5. As shown, forall delays excluding the maximum, schemes I and II outperform closedloop power control. The ARIB proposal only outperforms the others at thelowest delay (D=1).

Graphs 126, 128 depict the results for an α set using Equation 7 withD_(max) equal to seven. As shown, schemes I and II outperform bothclosed loop and the ARIB proposal at all delays, D.

What is claimed is:
 1. A method for controlling transmission powerlevels in a spread spectrum time division duplex communication systemhaving frames with time slots for communication, the method comprising:receiving at a first communication station communications from a secondcommunication station and transmitting from the first station powercommands based on in part a reception quality of the receivedcommunications; transmitting from the first communication station afirst communication having a transmission power level in a first timeslot; receiving at the second communication station the firstcommunication and the power commands; measuring a power level of thefirst communication as received; determining a pathloss estimate basedon in part the measured received first communication power level and thefirst communication transmission power level; setting a transmissionpower level for a second communication in a second time slot from thesecond station to the first station based on in part the pathlossestimate weighted by a quality factor and the power commands, whereinthe quality factor is a function of a time separation of the first andsecond time slots; and determining a quality, α, of the pathlossestimate based on in part a number of time slots, D, between the firstand the second time slot; and wherein the quality factor is α.
 2. Themethod of claim 1 wherein a maximum time slot delay is D_(max) and thedetermined quality, α, is determined by α=1−(D−1)/(D _(max)−1).
 3. Themethod of claim 1 wherein a maximum allowable time slot delay isD_(max-allowed) and the determined quality, α, is determined byα=max{1−(D−1)/(D _(max-allowed)−1),0}.
 4. The method of claim 1 whereinthe setting of the transmission power level is based on in part adesired received power level at the first station, a closed loop factorand an open loop factor; wherein the closed loop factor is based on inpart the received power commands and the open loop factor is based on inpart the pathloss estimate weighted by the quality factor.
 5. The methodof claim 1 wherein the setting of the transmission power level is basedon in part a desired received power level at the first station and acombined closed loop/open loop factor; wherein the combined closedloop/open loop factor is based on in part the received power commandsand the pathloss estimate weighted by the quality factor.
 6. The methodof claim 4 wherein the closed loop factor is updated for each receivedpower command.
 7. The method of claim 5 wherein the combined factor isupdated for each received power command.
 8. The method of claim 4wherein the desired received power level is based on in part a targetsignal to interference ratio and a measured interference level at thefirst station.
 9. The method of claim 5 wherein the desired receivedpower level is based on in part a target signal to interference ratioand a measured interference level at the first station.
 10. The methodof claim 1 wherein the first station is a base station and the secondstation is a user equipment.
 11. The method of claim 1 wherein the firststation is a user equipment and the second station is a base station.12. A spread spectrum time division duplex communication system having afirst and second communication station, the system using frames withtime slots for communication, the system comprising: the first stationcomprising: means for receiving communications from the secondcommunication station and transmitting power commands based on in part areception quality of the received communications; and means fortransmitting a first communication having a transmission power level ina first time slot; and the second station comprising: means forreceiving the first communication and the power commands; means formeasuring a power level of the first communication as received; meansfor determining a pathloss estimate based on in part the measuredreceived first communication power level and the first communicationtransmission power level; and means for setting a transmission powerlevel for a second communication in a second time slot from the secondstation to the first station based on in part the pathloss estimateweighted by a quality factor and the power commands, wherein the qualityfactor is a function of a time separation of the first and second timeslots; and wherein the second station further comprises means fordetermining a quality, α, of the pathloss estimate based on in part anumber of time slots, D, between the first and second time slot; and thequality factor is α.
 13. The system of claim 12 wherein a maximum timeslot delay is D_(max) and the determined quality, α, is determined byα=1−(D−1)/(D _(max)−1).
 14. The system of claim 12 wherein a maximumallowed time slot delay is D_(max-allowed) and the determined quality,α, is determined by α=max{1−(D−1)/(D _(max-allowed)−1),0}.
 15. Thesystem of claim 12 wherein the setting means sets the transmission powerlevel based on in part a desired received power level at the firststation, a closed loop factor and an open loop factor, the closed loopfactor is based on in part the received power commands and the open loopfactor is based on in part the pathloss estimate weighted by the qualityfactor.
 16. The system of claim 12 wherein the setting means sets thetransmission power level based on in part a desired received power levelat the first station and a combined closed loop/open loop factor, thecombined closed loop/open loop factor is based on in part the receivedpower commands and the path loss estimate weighted by the qualityfactor.
 17. The system of claim 15 wherein the closed loop factor isupdated for each received power command.
 18. The system of claim 16wherein the combined factor is updated for each received power command.19. The system of claim 15 wherein the desired received power level isbased on in part a target signal to interference ratio and a measuredinterference level at the first station.
 20. The system of claim 16wherein the desired received power level is based on in part a targetsignal to interference ratio and a measured interference level at thefirst station.
 21. The system of claim 12 wherein the first station is abase station and the second station is a user equipment.
 22. The systemof claim 12 wherein the first station is a user equipment and the secondstation is a base station.
 23. A communication station having itstransmission power level controlled in a spread spectrum time divisionduplex communication system, the system using frames with time slots forcommunication and having a second communication station transmitting afirst communication in a first time slot and power commands, thecommunication station comprising: at least one antenna for receiving thefirst communication and the power commands and transmitting an amplifiedsecond communication in a second time slot; a channel estimation devicehaving an input configured to receive the received first communicationfor producing channel information; a data estimation device havinginputs configured to receive the received first communication, the powercommands and the channel information for producing soft symbols andrecovering the power commands; a power measurement device having aninput configured to receive the channel information for producing ameasurement of a received power level; a pathloss estimation devicehaving an input configured to receive the measured received power levelfor producing a pathloss estimate for the first communication; a qualitymeasurement device for producing a quality measurement based at least inpart upon a time separation of the first time slot and a second timeslot; a transmit power calculation device having inputs configured toreceive the pathloss estimation, the recovered power commands and thequality measurement for producing a power control signal based on inpart the pathloss estimate weighted by the quality measurement and therecovered power commands; and an amplifier having inputs configured toreceive the power control signal and a second communication to betransmitted in the second time slot for amplifying the secondcommunication in response to the power control signal to produce theamplified second communication.